Create a function returning an int of a chosen tuple

SQL/plpgsql/create_biggest_ordered_quantity.sql

@@ -0,0 +1,11 @@
+CREATE OR REPLACE FUNCTION biggest_ordered_quantity() RETURNS INTEGER AS 
+$$
+DECLARE
+    ans INTEGER;
+BEGIN
+    SELECT ori_quantity FROM OrderedItem WHERE ori_id = 1 INTO ans;
+
+    RETURN ans;
+END;
+$$
+LANGUAGE plpgsql;